Central Campus Air Quality Model (CCAQM) Instructions
Effective
Stack Height
Plumes
rise vertically from a smokestack before starting to disperse
according to the Gaussian model (see figure below). Therefore,
because of the plume rise, the centerline of the Gaussian model is
higher than the height of the stack. The “effective stack height”,
which is stack height plus vertical plume rise, is used in the
Gaussian model for more accurate calculations of pollution
concentration from a point source.
Plume Rise and Effective Stack Height
Calculating
Effective Stack Height Wind Speed
The surface wind speed is different at
the effective stack height, which is used in the Gaussian model.
To determine the effective stack height wind speed, U_{H},
use the following equation and table.
Where:

U_{a} = wind speed at
altitude Z_{a}, m/s

H = effective stack height, m

Z_{a}= height above
surface, m (usually 10 meters)

p = exponent is a function of
atmospheric stability class
Stability Class 
Description 
Exponent p 
A 
Very unstable 
0.15 
B 
Moderately unstable 
0.15 
C 
Slightly unstable 
0.20 
D 
Neutral 
0.25 
E 
Slightly Stable 
0.40 
F 
Stable 
0.60 
